The invention relates to catheters with varying physical properties long their length such as varying degrees of rigidity. More specifically, the invention relates to catheters as well as methods and devices for their manufacture wherein the catheters are made with streams of at least two materials which are co-extruded to form a final extrusion profile having a plurality of longitudinally disposed sections of varying composition.
Methods and devices have been proposed for the manufacture of extrusion profiles having variable properties along the length thereof such as varying degrees of rigidity. One such extrusion profile has been proposed having distinct longitudinal sections with each section made of a different material, thereby varying certain properties along the length of the extrusion profile. Another approach is to have circumferentially divided material strips for increasing the stiffness of the tubing. The strips are continuous and extend along the longitudinal axis of the extrusion profile, but are encapsulated by a softer biocompatible base material. In still another approach, blow molding techniques are utilized in the manufacture of a hollow plastic product which varies somewhat in composition, combining two different thermoplastic resin materials to form a single hollow plastic product.
It would be desirable to manufacture an extrusion profile such as a catheter, for example, having areas of differing material compositions and wherein the overall composition of the profile varies along its longitudinal axis, resulting in varying properties at different cross sectional portions of the profile. It would also be desirable to be able to provide the aforementioned profile in the manufacture of catheters for use in angiographic applications, for example. Preferably, these catheters would be pliable or of limited stiffness at the distal end thereof in order to easily follow the course of a blood vessel while being of a more rigid consistency at the proximal end of the catheter to convey pressure exerted on the catheter to its distal end. It would also be advantageous to manufacture catheters, as described herein, using an extrusion device capable of providing streams of molten material wherein certain streams can be easily turned on or off to selectively produce within one length of the extrusion profile a number of sections having somewhat different physical properties.
The present invention overcomes the shortcomings of the prior art by providing certain types of extrusion profiles such as catheters as well as a method and device for their manufacture. In accordance with the invention, catheters are manufactured by an extrusion process whereby streams of molten material are combined to form a single extrusion profile and wherein one or more of the streams can be turned on or off during the process to produce within one length of the extrusion profile a number of sections wherein certain physical properties are altered from one section to the next.
Catheters of the invention are manufactured to include longitudinal bands of different materials. The catheter is manufactured by simultaneously extruding a plurality of divided streams of molten material and conveying the aforementioned streams simultaneously through a molding nozzle where they are joined to form a catheter made of at least two different materials. Each of the streams is conveyed through an extrusion nozzle to feeder lines. At least some of the feeder lines can be turned on and off in a controlled manner to control the longitudinal extent of the individual streams within the finished catheter. The cross sections of one or more of the individual streams can be reduced while the cross section of an adjoining band can be increased correspondingly to vary the physical properties such as the stiffness or rigidity of the catheter.
In this manner, physical characteristics of the catheter catheter can be controlled by including certain selected materials within the wall of the catheter. Stiffer materials, for example, can be incorporated in certain sections of the catheter to provide additional stiffness along a portion of the catheter as desired. Angiographic catheters, for example, can be manufactured to be more pliable or of more limited stiffness at the distal end thereof to thereby permit the catheter to easily follow the course of a blood vessel. The proximal end of such a catheter can be manufactured with stiffer materials to convey pressure to its distal end. Fiber bundles can also be incorporated into the extrusion profile during the extrusion process in order to position materials of greater stiffness within the manufactured catheter.
A device for the manufacture of catheters according to the invention includes at least a pair of extruders each of which supplies a plurality of material strips to a single molding nozzle where the materials converge to form an extrusion profile such as a catheter, for example. Distribution lines from at least one of the extruders are provided with cut off valves to increase or decrease the flow of material forming individual material strips. The two extruders can supply two different materials which are combined through a molding nozzle to form a single extrusion profile. Physical properties such as stiffness can be varied in the extrusion profile by controlling the material flow from at least one of the extruders. For example, one or more strips of material from one of the extruders can be eliminated by closing the appropriate cut off valves in the control lines coming from the extruder. The presence or absence of certain material strips will determine the stiffness of the finished extrusion profile as those skilled in the art will appreciate.
It is accordingly an object of the present invention to provide certain extrusion profiles such as catheters, for example, and a method for their manufacture.
It is another object of the present invention to provide an apparatus for the manufacture of certain extrusion profiles such as catheters and the like.
It is still another object of the present invention to provide extrusion profiles such as catheters as well as a method and apparatus for their manufacture wherein the catheters are manufactured from a plurality of strips of different materials to form a finished extrusion profile having varying physical properties along the longitudinal extent thereof.
These and other objects of the invention will be more apparent to those skilled in the art following a review of the remainder of the disclosure including the detailed description of the preferred embodiment and the appended claims.